Security institutions such as prisons, mental hospitals, etc., require strict control of keys. In the example of a prison, guards must be especially cautious to maintain control of his or her keys. Unauthorized removal of a key could result in a serious, even life threatening, predicament.
It is therefore desirable to assist guards or others charged with maintaining security keys to (a) hold a key secure and to (b) assist the individual remember the present location of the key and, following use, to encourage quick re-securement of the key.
Various apparatus has been developed to warn that keys have been misplaced. For example, U.S. Pat. No. 4,558,307 to Leinart van Lidt de Jeude discloses a reminder device that may be attached to a key, wallet, etc. It includes an electronic circuit with a time delay arrangement connected to a photo sensitive audio signalling device that functions to emit an audible signal after the reminder device has been irradiated by ambient radiation for a selected period of time. The device is attached directly to the key and hence travels with the key.
U.S. Pat. No. 4,012,732 to Herrick discloses a security device in which an inanimate object such as a key is placed in a receptacle for free access. The receptacle is connected to a clock that is set to operate an alarm following a predetermined time interval if a sensor does not detect human activity in the area of the receptacle. Sensors are provided to detect the presence of the key in the receptacle and operate when the key is removed from the receptacle to override the alarm after the predetermined time period has passed.
U.S. Pat. No. 4,652,865 to Maharshak discloses a credit card holder warning device in which credit cards are received in a holder including opposed card cover surfaces. The surfaces include electrical contact strips that make electrical contact when a credit card is withdrawn from the carrier. The card holder includes a timer and alarm that are switched on and off by the contacts. The timer delays the operation of the alarm for a set time sufficient to complete a transaction. After the prescribed transaction time period, the alarm device is actuated, indicating to the user that the card has not been returned to the card holder. Apart from the card holder, there is no device selectively securing the card in position within the holder or for securing the holder to the user.
U.S. Pat. No. 4,719,453 to Beck et al. discloses a card carrier alarm somewhat similar to the Maharshak reference described above with the exception that the Beck apparatus does not include a timer and includes further provisions for triggering an alarm when the card is missing from the carrier and the carrier is placed in a pocket or purse.
The above apparatus are not addressed to the problem of providing a security device for a key in which the key may be secured against unauthorized removal when not in use, and which will produce an audible or otherwise detectable signal after the key has been removed for a selected time interval.
It is therefore an object of the present invention to provide a key security device in which provisions are made both to secure a key against unintended or unauthorized removal, and to produce a detectable alarm after the key has been removed for a selected period of time.
It is a further object to provide such a device in which the selected period of time may be selectively reset by the user without returning the key to the security device.
A still further object is to provide such a device in which the security device itself may be secured to a user.
These and other objects and advantages will become apparent upon reading the following detailed description which, taken with the accompanying drawings, describe a preferred form of the present invention.